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Bonding properties in the crystal of 4,5-dichloro-l,2,3-dithiazolium chloride (Appel's salt) were studied using a combination of single-crystal high-resolution X-ray diffraction data and the orbital-free quantum crystallography approach. A QTAIM-based topological model shows the proximity of S—C and S—N bonds to the sesquialteral type and establishes the low S—S bond order in the l,2,3-dithiazolium heterocycle. It is found that the electrostatic potential carries the traces of a common positive area on the junction of interatomic zero-flux surfaces of S1 and S2 atomic basins; meanwhile the exchange energy density per particle shows perfectly here two separate minima through which the two bond paths run. Thus, the pair intermolecular interactions Cl−...S1 and Cl−...S2 formed by the common chloride anion placed near the center of the S—S bond are categorized as chalcogen bonds.

Crystalline chalcogenazinoquinolinium monoiodides, where the chalcogen atom is oxygen and sulfur, were studied using a combination of X-ray diffraction, Raman and UV-vis spectroscopies and photoluminescence experimental techniques. Periodic quantum-chemical calculations were performed to characterize the features of electronic structure and vibrational assignment. X-ray diffraction and Raman spectroscopy experiments consistently reveal phase transition of thiazinoquinolinium monoiodide at low temperatures with the decrease of symmetry to P 1. The luminescence study for oxazinoquinolinium monoiodide reveals the excitation maximum at 532 nm and emission at 650 nm with significantly higher intensity than for the thiazinoquinolinium derivative. The studied chalcogenazinoquinolinium monoiodides demonstrate high values of Stokes shift up to 150 nm.

Treatment of 4-phenyl-5H-1,2,3-dithiazole-5-thione with iodine in acetonitrile yielded crystalline product with thione-iodonium three-center halogen bond and triiodide anion bound with two iodine molecules by the typical halogen bonds. At the level of a theoretical study of electron density and its gradients, the similarity of electronic properties of the central iodine atom in bridged moiety [S−I−S]+ and in triiodide anion [I−I−I]− has been illustrated. The experimental and theoretical Raman spectra of iodonium salt are discussed: the assignment of the bands corresponding to the iodonium bridged fragment vibrations has been made on the basis of calculated ab initio data.

I.D. Yushina, iushinaid@susu.ru E.V. Bartashevich, bartashevichev@susu.ru South Ural State University, Chelyabinsk, Russian Federation. Юшина Ирина Дмитриевна – кандидат химических наук, научный сотрудник, НИЛ мно- гомасштабного моделирования многокомпонентных функциональных материалов НОЦ «Нано- технологии», Южно-Уральский государственный университет. 454080, г. Челябинск, проспект Ленина, 76. E-mail: iushinaid@susu.ru Барташевич Екатерина Владимировна – доктор химических наук, доцент, заведующий НИЛ многомасштабного моделирования многокомпонентных функциональных материалов НОЦ «Нанотехнологии», профессор кафедры «Теоретическая и прикладная химия», Южно-Уральский государственный университет. 454080, г. Челябинск, проспект Ленина, 76. E-mail: bartashevichev@susu.ru Methodological features of the crystal structure modeling for compounds with three-center halogen bond formed by two electron donors S–I+–S in polyiodide crystals were considered within the framework of periodic calculations based on localized atomic orbitals. The analysis of applying the different basis sets, effective core potentials, density functional theory functionals, and Grimme dispersion corrections revealed their effect on the geometric, electronic and vibrational properties obtained in calculations. Distribution of S-I bond lengths in S–I+–S fragment was analyzed. The effect of hybrid functional was demonstrated in the significant elongation of S-I distance. The treatment of dispersion interactions via Grimme approach did not significantly influence obtained results. The calculated vibration modes in medium wavenumber region of characteristic cationic stretching vibrations were validated according to experimental Raman spectra and were found to be in good agreement for C-N, C-C and C=S stretching vibrations. Small-core effective potential was shown to be effective for representation of bond lengths in S–I+–S fragment and gave reasonable results for vibrational data for cationic stretching vibrations. Taking into account relativistic effect on the level of basis set led to fine reproducibility of S-I bond lengths although in polyiodides of complex structure it should be treated with caution due to possible incorrect representation of interanionic distances. Методологические особенности моделирования кристаллической структуры соединений с трехцентровой галогенной связью S–I+–S, образованной двумя донорами электронов в кристаллах полииодидов рассматривались в рамках периодических квантово- механических расчетов на основе локализованных атомных орбиталей. Анализ применения различных базисных наборов, эффективных остовных потенциалов, функционалов в теории функционала плотности и дисперсионных поправок по Гримме выявил особенности влияния выбора метода на геометрические, электронные и колебательные свойства, полученные в расчетах. Эффект влияния гибридного функционала проявлялся в значительном удлинении связи S–I. Учет дисперсионных взаимодействий на уровне эмпирической поправки Гримме существенно не влиял на качество получаемых данных. Рассчитанные моды колебаний в области средних волновых чисел характерных катионных валентных колебаний проверены на соответствие с экспериментальными спектрами комбинационного рассеяния, показано хорошее соответствие, в том числе для валентных колебаний C–N, C–C и C=S. Малоостовный потенциал продемонстрировал хорошие результаты в воспроизведении длин связей в S–I+–S фрагменте и колебательных характеристик в области валентных колебаний в катионе. Учет релятивистских эффектов на уровне базисного набора позволил воспроизвести длины S–I связей в кристалле, однако применение этого расчетного приближения для полииодидов сложного строения должно производиться с осторожностью из-за возможного искажения расстояний между полииодидными субъединицами. This study is supported by RFBR № 20-03-00240

The reaction of 1-methyl-3-methylthio-5-phenyl-1,2,4-triazinium (MTPT) iodide with diiodine in a solution leads to monoiodide crystal structure that in excess of iodine gives the unusual tetraiodide anion with two central iodine atoms in disorder. The bonding within the anion has been characterized as I–…I2…I–; the existence of the bound iodine molecule inside has been proven by the characteristic band in experimental and calculated Raman spectra. Non-covalent interactions of MTPT in considered crystal structures are different. Monoiodide anion as a strong electron donor allows the formation of the S…I chalcogen bonds that are absent in tetraiodide structure. The features of halogen bonds within the I42– anion are also performed.

A series of crystalline thiazoloquinolinium iodides has been studied using a combination of thermal analysis, mass and Raman spectroscopy techniques. The influence of composition and polyiodide anion stoichiometry on the features of iodine loss has been revealed. It has been shown that the existence of a bound diiodine molecule in a polyiodide chain leads to significant decrease in melting point and decomposition temperatures in comparison with corresponding mono- and triiodide salts. The loss of the diiodine molecule from the complex polyiodide proceeds independently, without decomposition of the organic cation, while the release of diiodine from the triiodide anion goes simultaneously with thermal decomposition of the cation. In addition, the decomposition processes on the surface of the thiazoloquinolinium polyiodide crystal have been investigated during sample storage. Iodine loss and formation of more stable triiodide have been proved using Raman spectroscopy data.

Diversity of mutual orientations of Y–S and I–X and covalent bonds in molecular crystals complicate categorizing noncovalent chalcogen and halogen bonds. Here, the different types of S...I interactions with short interatomic distances are analysed. The selection of S...I interactions for the categorization of the chalcogen and halogen bonds has been made using angles that determine the mutual orientation of electron lone pairs and σ-holes interacted S and I atoms. In complicated cases of noncovalent interactions with `hole-to-hole' of S and I orientations, distinguishing the chalcogen and halogen bonds is only possible if the atom is uniquely determined, which also provides the electrophilic site. The electronic criterion for chalcogen/halogen bonds categorizing that is based on analysis of dispositions of electron density and electrostatic potential minima along the interatomic lines has been suggested and its effectiveness has been demonstrated.

The insight into the behavior of polyiodides under non-ambient conditions can enrich the practical applications due to obtaining materials with adjustable and tunable conducting properties. In this work Raman spectroscopy study in the range 0 – 6.5 GPa has been performed for dithiazolylidene-dithiazolium zigzag polyiodide with N-H…N hydrogen bond. Variations of band positions in the low-wavenumber region of Raman spectra have been attributed to the changes in the anionic part of the unit cell. The association of different interacting polyiodide subunits at pressure above 1.5 GPa leads to the emergence of the bands at 98 and 115 cm-1 due to consistent vibrations in the I82- zigzag. The emergence of the band at 159 cm-1 above 0.28 GPa can be assigned to N-H…N hydrogen bond vibration. The obtained results depict undergoing structure transformations: the stronger are cation…cation and anion…anion interactions the more likely is the observation of conducting properties due to the formation of polyiodide zigzag and strongly-bound hydrogen-bonded fragment.

Recently, we proposed a computational design strategy for organic nonlinear optical materials, based on the global minimization of lattice energy to predict the crystal packing from the first principles. Here, we validate this strategy on triiodobenzenes, which include CH···I hydrogen and I···I halogen bonding as the structure-determining components of their intermolecular interactions. To refine the van der Waals (vdW) parameters for an I atom, the ab initio potential surfaces for the model dimers were calculated at the CCSD(T)/cc-pVTZ + CP theory level. The hydrogen bond C–H···I was found to have an interaction energy of −0.5 kcal/mol. The I···I contact of type I (140°–140°) was found to be attractive with a well depth of −0.4 kcal/mol at a 4.6 A distance, whereas type II contact (180°–90°) was found to be nearly twice more attractive. Its potential well depth reaches −0.7 kcal/mol at an I···I distance of 4.4 A. These binding energies are therefore weaker than that of the typical hydrogen bonds. The AMO...

Computational methods can potentially accelerate development of more efficient organic materials for second harmonic generation. Here, we test the method that includes the evolutionary algorithm for predicting crystal structure and prognosis of nonlinear optical properties based on the predicted structure. For this test, we selected 2-iodo-3-hydroxypyridine, which exhibits second harmonic generation intensity comparable to that of urea. We performed global minimization of the lattice energy and found the experimental structure when many-body dispersion correction is added to the density functional theory values. We analyzed geometric preferences of the halogen bonding in predicted virtual polymorphs. We also found linear correlation between the lengths of the iodine–iodine halogen bonds and calculated second order susceptibilities.

The photolysis products of the [Rh(NH3)5(NO2)](NO3)2 complex in aqueous solutions were studied by electron paramagnetic resonance (EPR), UV-visible (UV-vis), and 15N nuclear magnetic resonance (15N NMR) spectroscopies. Aqueous solutions of [Rh(NH3)5(NO2)](NO3)2 became blue when exposed to UV irradiation under an oxygen-containing atmosphere while aqueous solutions of [Rh(NH3)5(NO2)](NO3)2 with additives of NaNO2 turned orange under the same conditions. Photolysis of degassed [Rh(NH3)5(NO2)](NO3)2 solutions did not lead to any change of their color. It was suggested that, as a result of the photolysis, the complex decomposed with the formation of a NO2 fragment and a fragment containing Rh(II). In the presence of molecular oxygen in solution, a superoxide complex, [Rh(NH3)5O2]2+, was formed, in which electron transfer from the metal ion to O2 took place.

The modern concepts on specific features of anisotropy of the electron density of valence shells of bound atoms and chemical bonds providing the successful description of the properties of halogen bonds formed by the iodine molecule in compounds with useful physicochemical properties are generalized in the review. The prognoses of basicity by the diiodine basicity scale for the nitrogen-containing compounds are illustrated. The regularities and peculiarities of shifting bands in Raman spectra of iodine-containing organic crystals are considered. The methodical and specific problems of modeling appeared when the electronic characteristics of the iodine compounds are estimated and briefly discussed.

The crystal structure and properties of (Z)-4-chloro-5-((2-((4-chloro-5H-1,2,3-dithiazol-5-ylidene)amino)phenyl)amino)-1,2,3-dithiazol-1-ium oligoiodide (C2/c) synthesized from the initial bis(4-сhloro-5H-1,2,3-dithiazolo-5-ylidene)benzene-1,2-diamine (P21/c) have been characterized by various experimental and theoretic methods. The superposition of atomic basin boundaries in the electron density and in the electrostatic potential does not confirm the halogen bonding between the triiodide anion and sulfur atoms in cation. On the other hand, in the studied oligoiodide, the charge-assisted iodine–iodine halogen bonds are observed between the strongly asymmetric triiodide and diiodine units; thus, the oligoiodide anion includes at least two diiodine fragments with bond lengths 2.7334(4) and 2.7786(5) A bound. This key trait has resulted in characteristic spectral and thermal features. Raman spectra do not contain typical triiodide bands but only those that are expectable for bound diiodine at 157 and 179 cm−1. Thermal decomposition has demonstrated release of both diiodine molecules within one decomposition stage without melting.

To understand what tools are really suitable to identify and classify the iodine–iodine non-covalent interactions in solid organic polyiodides, we have examined the anisotropy of the electron density within the iodine atomic basin along and across the iodine–iodine halogen bond using the Laplacian of electron density, one-electron potential and electron localization function produced by Kohn–Sham calculations with periodic boundary conditions. The Laplacian of electron density exhibits the smallest anisotropy and yields a vague picture of the outermost electronic shells. The one-electron potential does not show such a deficiency and reveals that the valence electron shell for the halogen-bond acceptor iodine is always wider than that for the halogen-bond donor iodine along its σ-hole direction. We have concluded that the one-electron potential is the most suitable for classification of the iodine–iodine bonds and interactions in complicated cases, while the electron localization function allows to distinguish the diiodine molecule bonded with the monoiodide anion from the typical triiodide anion.

The interrelation between noncovalent bonds and physicochemical properties is in the spotlight due to the practical aspects in the field of crystalline material design. Such study requires a number of similar substances in order to reveal the effect of structural features on observed properties. For this reason, we analyzed a series of three substituted thiazolo[2,3-b][1,3]thiazinium triiodides synthesized by an iodocyclization reaction. They have been characterized with the use of X-ray diffraction, Raman spectroscopy, and thermal analysis. Various types of noncovalent interactions have been considered, and an S&hellip, I chalcogen bond type has been confirmed using the electronic criterion based on the calculated electron density and electrostatic potential. The involvement of triiodide anions in the I&hellip, I halogen and S&hellip, I chalcogen bonding is reflected in the Raman spectroscopic properties of the I&ndash, I bonds: identical bond lengths demonstrate different wave numbers of symmetric triiodide vibration and different values of electron density at bond critical points. Chalcogen and halogen bonds formed by the terminal iodine atom of triiodide anion and numerous cation&hellip, cation pairwise interactions can serve as one of the reasons for increased thermal stability and retention of iodine in the melt under heating.

This work is devoted to the discussion of structural changes in crystalline iodine under low temperature studied from experimental and theoretic points of view. Experimental Raman spectra in the temperature range 5-300 K demonstrated unusual behavior of stretching vibration at ∼180 cm-1 with temperature. The data allowed obtaining of ω( T) functions for both external translational and internal stretching modes of I2. It was found that ω( T) trends significantly differ in comparison to typical van der Waals crystal α-S8. The observed anomalies are explained from a theoretic point of view because of the strengthening of intralayer halogen bonding between I2 molecules.

The crystal structure of (E)-8-((2,3-diiodo-4-(quinolin-8-ylthio)but-2-en-1-yl)thio)quinolin-1-ium triiodide, determined at 100 K in the space group C2/c, contains the bridge hydrogen bond [N···H···N]+ linking two neighboring quinolinium fragments; the distance N···N is 2.6927(15) A. The experimental difference Fourier maps at 293 and 100 K lead to a conclusion about the dynamic nature of the H atom disorder. Calculated vibrational modes obtained for the same compound in the space groups C2/c and Cc are in agreement with the experimental Raman spectrum in the low-frequency region; together, they are consistent with a previous supposition about the dynamic nature of the H atom disorder. We have found that the cation–anion interactions are realized through the charge-assisted iodine–iodine halogen bond.

Two kinds of iodine–iodine halogen bonds are the focus of our attention in the crystal structure of the title salt, C12H8ClINO+·I3−, described by X-ray diffraction. The first kind is a halogen bond, reinforced by charges, between the I atom of the heterocyclic cation and the triiodide anion. The second kind is the rare case of a halogen bond between the terminal atoms of neighbouring triiodide anions. The influence of relatively weakly bound iodine inside an asymmetric triiodide anion on the thermal and Raman spectroscopic properties has been demonstrated.

Various structural features, such as proton disorder or noncovalent interactions, determine the existence of switchable nonlinear optical properties under varying external conditions. Thus, for the single crystal of diiodobutenyl-bis-thioquinolinium triiodide with the bridge hydrogen atom, previously characterized under ambient conditions by C2/c symmetry, we have measured Raman spectra in the temperature range from 298 K down to 113 K. Variations in low-wavenumber region of Raman spectra at temperatures below 153 K have been attributed to the change of the bridge hydrogen atom position in the [NHN]+ fragment, thus lowering the crystal symmetry from C2/c to Cc. Quantum chemical calculations in the solid state for noncentrosymmetric Cc structure predict high hyperpolarizability and second-order electric susceptibilities, comparable to those of modern nonlinear optical materials. This indicates the emergence of nonlinear optical properties in the low-temperature phase of the studied crystal. Copyright © 2017 John Wiley & Sons, Ltd.

A number of new solid polyiodides of thia- and oxa-zinoquinolinium derivatives have been characterized using a combined approach of Raman spectroscopy and periodic 3D calculations of the Raman intensities. Various cation–anion ratios, including tri- and polyiodides of the complex structure [I3⋯I2]−, have been studied. For the oriented single crystal containing the [I3⋯I2]− fragments, the polarized Raman spectra and the angular dependency of the band intensities on crystal rotation have been obtained. These techniques have allowed us to get new information on the spatial organization of the intermolecular interactions of iodine in polyiodide-anion chains. They have also shown perspectives on the geometrical characterization of complex polyiodides using Raman spectroscopy.

The study focuses on the energy and quantum topological properties of substituted 2- and 8-allylthioquinoline complexes with iodine, which are assumed to correspond to prereaction states in the iodocyclization reaction leading to the formation of thiazolo- and tiazinoquinoline systems. The structures of the complexes and the corresponding atomic interactions are modeled considering the different conformational states of allyl-substituted quinolinethiols (thioquinolines). The energy values are analyzed for the interactions between the iodine molecule and different donor centers of the substituted quinoline system: the nitrogen heteroatom, sulfur, and π-system of the allyl group. It is shown that the formation of stable complexes with the nitrogen of the quinoline ring is complicated by steric hindrances posed by the S-allyl group at positions 2 and 8 of the quinoline system, which in turn contributes to the convergence of the cyclization centers.

Iodocyclization products of 2-allylthioquinoline are obtained in the form of polyiodides with different stoichiometric compositions. X-ray crystallography data are analyzed for two different crystal structures of 1-iodomethyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium polyiodides: triiodide C12H11INS+I 3 − and complex polyiodide 2(C12H11INS+I 3 − )·I2. A comparison is made of the nonbonding interactions of dihydrothiazoloquinolinium with atoms of the triiodide anion and complex polyiodide to show the crystal structure features attributed to the participation of molecular iodine.

The dielectric properties of tetramethylammonium monoiodide and pentaiodide were investigated in broad temperature range ([Formula: see text]C till [Formula: see text]C). It was demonstrated that the structural organization of the polyiodide chain containing I[Formula: see text][Formula: see text][Formula: see text]I charge-assisted halogen bonds influenced the parameters and the mechanism of electric conductivity of considered compound. The impedance spectroscopic measurements revealed that the direct current electric conductivity of pentaiodide salt is around four orders of magnitude higher than that of corresponding monoiodide. Moreover, pentaiodide demonstrates the hopping mechanism of conductivity.

Development of new materials and drugs presently requires trial chemical methods that are time consuming and that depends on the chance more than we would have liked. We aim to describe, how the high throughput calculations can be applied for computational predictions of the organic crystalline structure and its properties. In this work we tried to illustrate the examples of techniques that were applied to accelerate the design of iodine-contained organic materials with nonlinear optical properties, to explain the plasticity of maleate amino acids crystals by means of analysis of hydrogen bonds orientation, to clarify the biological activity of traditional antibiotics using molecular dynamics modeling

C13H11I4NS, monoclinic, C2/c (no. 15), a = 29.508(1) Å, b = 8.3747(3) Å, c = 14.9533(5) Å, β = 105.945(4)°, V = 3553.1 Å3, Z = 8, Rgt(F) = 0.056, wRref(F2) = 0.0705, T = 120 K., We thank financial support from Spanish Ministerio de Economía y Competitividad (MAT2010-15094, FPUgrant AP2008-03942 to A.D.) and EDRF. This work was supported by the Russian Ministry for Education and Science.